U.S. patent number 10,551,573 [Application Number 16/374,011] was granted by the patent office on 2020-02-04 for fiber optic connector sub-assemblies and fiber optic connectors including the same.
This patent grant is currently assigned to Corning Optical Communications LLC. The grantee listed for this patent is CORNING OPTICAL COMMUNICATIONS LLC. Invention is credited to Adra Smith Baca, Rebecca Lynn Burt, Jeffrey Dean Danley, Darrin Max Miller, Dennis Craig Morrison.
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United States Patent |
10,551,573 |
Baca , et al. |
February 4, 2020 |
**Please see images for:
( Certificate of Correction ) ** |
Fiber optic connector sub-assemblies and fiber optic connectors
including the same
Abstract
A fiber optic connector sub-assembly includes a ferrule having a
front end, a rear end, and a ferrule bore extending between the
front and rear ends along a longitudinal axis. The fiber optic
connector sub-assembly also includes a bonding agent disposed in
the ferrule bore and having first and second ends along the
longitudinal axis. The bonding agent has been melted and solidified
at the first and second ends without there being an optical fiber
present in the ferrule bore.
Inventors: |
Baca; Adra Smith (Hickory,
NC), Burt; Rebecca Lynn (Painted Post, NY), Danley;
Jeffrey Dean (Hickory, NC), Miller; Darrin Max (Hickory,
NC), Morrison; Dennis Craig (Lincolnton, NC) |
Applicant: |
Name |
City |
State |
Country |
Type |
CORNING OPTICAL COMMUNICATIONS LLC |
Hickory |
NC |
US |
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Assignee: |
Corning Optical Communications
LLC (Charlotte, NC)
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Family
ID: |
58056545 |
Appl.
No.: |
16/374,011 |
Filed: |
April 3, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190227243 A1 |
Jul 25, 2019 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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15901151 |
Feb 21, 2018 |
10274685 |
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PCT/US2016/045783 |
Aug 5, 2016 |
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14886905 |
Feb 28, 2017 |
9581768 |
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62208131 |
Aug 21, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09J
171/08 (20130101); C09J 179/08 (20130101); G02B
6/3861 (20130101); C09J 181/04 (20130101); C09J
161/02 (20130101) |
Current International
Class: |
G02B
6/38 (20060101); C09J 161/02 (20060101); C09J
181/04 (20060101); C09J 179/08 (20060101); C09J
171/08 (20060101) |
Field of
Search: |
;385/80 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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59109014 |
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Jun 1984 |
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JP |
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2014013410 |
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Jan 2014 |
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JP |
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Primary Examiner: Blevins; Jerry M
Attorney, Agent or Firm: Banakar; Kapil U.
Parent Case Text
PRIORITY APPLICATIONS
This application is a continuation of U.S. application Ser. No.
15/901,151, filed on Feb. 21, 2018, which is a continuation of PCT
Application No. PCT/US2016/045783, filed on Aug. 5, 2016, which is
a continuation of U.S. application Ser. No. 14/886,905, filed Oct.
19, 2015, now U.S. Pat. No. 9,581,768, issued on Feb. 28, 2017,
which claims the benefit of priority of U.S. Provisional
Application No. 62/208,131 filed on Aug. 21, 2015. The content of
each of these applications is relied upon and incorporated herein
by reference in its entirety.
Claims
What is claimed is:
1. A fiber optic connector sub-assembly, comprising: a ferrule
having a front end, a rear end, and a ferrule bore extending
between the front and rear ends along a longitudinal axis; and a
bonding agent disposed in the ferrule bore and having first and
second ends along the longitudinal axis, wherein: the bonding agent
has been melted and solidified at the first and second ends; at
least a portion of the bonding agent between the first and second
ends has not been melted and solidified; and an optical fiber is
not present in the ferrule bore.
2. The fiber optic connector sub-assembly of claim 1, wherein the
at least a portion of the bonding agent between the first and
second ends has not been melted and solidified comprises a powdered
material.
3. The fiber optic connector sub-assembly of claim 2, wherein the
powdered material comprises particles of the bonding agent, the
particles having an average size between about 5% and about 10% of
a minimum diameter of the ferrule bore.
4. The fiber optic connector sub-assembly of claim 1, wherein the
bonding agent that has been melted and solidified has a density
between about 1.0 g/cc and about 1.5 g/cc, and further wherein the
at least a portion of the bonding agent between the first and
second ends that has not been melted and solidified has a bulk
density that is less than 1.0 g/cc.
5. The fiber optic connector sub-assembly of claim 1, wherein the
bonding agent that has been melted and solidified has a density
between about 1.3 g/cc and about 1.4 g/cc, and further wherein the
at least a portion of the bonding agent between the first and
second ends that has not been melted and solidified has a bulk
density that between about 0.4 g/cc and about 0.6 g/cc.
6. The fiber optic connector sub-assembly of claim 1, wherein the
bonding agent that has been melted and solidified has a density
that is at least 1.5 times the bulk density of the bonding agent
between the first and second ends that has not been melted and
solidified.
7. The fiber optic connector sub-assembly of claim 1, wherein the
bonding agent has been melted and solidified in a peripheral region
of the bonding agent that is between the first and second ends and
in contact with the ferrule bore, the at least a portion of the
bonding agent between the first and second ends that has not been
melted and solidified being located in a central region of the
bonding agent that is surrounded by the peripheral region.
8. The fiber optic connector sub-assembly of claim 1, wherein the
bonding agent comprises a partially cross-linkable polymer resin
having a melting point between about 250.degree. C. and about
350.degree. C., and further wherein the bonding agent that has been
melted and solidified comprises the partially cross-linkable
polymer resin in a partially crystalline form.
9. The fiber optic connector sub-assembly of claim 8, wherein the
partially cross-linkable polymer resin is one chemical species
selected from the group consisting of a poly(phenylene sulfide), a
poly(phyenylene oxide), a polyamide-imide, a liquid crystal
polymer, a polyether ether ketone, and a cyclic olefin
copolymer.
10. The fiber optic connector sub-assembly of claim 8, wherein the
partially cross-linkable polymer resin comprises poly(phenylene
sulfide).
11. The fiber optic connector sub-assembly of claim 8, wherein the
bonding agent further comprises between about 0.1 to about 10 parts
by weight of a silane coupling agent per 100 parts of the partially
cross-linkable polymer resin.
12. The fiber optic connector sub-assembly of claim 1, wherein the
first and second ends of the bonding agent are part of respective
first and second regions of the bonding agent along the
longitudinal axis, the first region being closer to the front end
of the ferrule than the second region, and the first and second
regions each having an axial length between about 1% and 33% of an
overall axial length of the bonding agent, and further wherein at
least 90% of the bonding agent in the first and second regions has
been melted and solidified.
13. The fiber optic connector sub-assembly of claim 1, wherein the
ferrule bore includes a first section extending inwardly from the
rear end of the ferrule and having a first width, a second section
extending inwardly from the front end of the ferrule and having a
second width that is less than the first width, and a transition
section located between the first section and the second section,
further wherein the bonding agent is at least partially disposed in
the transition section.
14. The fiber optic connector sub-assembly of claim 13, wherein:
the first section of the ferrule bore is a cylindrical bore
extending from the rear end of the ferrule to the transition
section and the first width has a first diameter; the second
section of the ferrule bore is a cylindrical bore extending from
the front end of the ferrule to the transition section and the
second width has a second diameter; and the first diameter is at
least twice the second diameter.
15. The fiber optic connector sub-assembly of claim 14, wherein: an
axial length of the first section is greater than half of an axial
length of the ferrule; and an axial length of the second section is
greater than an axial length of the transition section and less
than a third of the axial length of the ferrule.
16. A fiber optic connector sub-assembly, comprising: a ferrule
having a front end, a rear end, a ferrule bore extending between
the front and rear ends along a longitudinal axis; and a bonding
agent disposed in the ferrule bore, wherein: the bonding agent
comprises a partially cross-linkable polymer resin; only some of
the bonding agent has been melted and solidified; the bonding agent
that has not been melted and solidified comprises particles in an
amorphous form; and an optical fiber is not present in the ferrule
bore.
17. The fiber optic connector sub-assembly of claim 16, wherein the
partially cross-linkable polymer resin has a melting point between
about 250.degree. C. and about 350.degree. C.
18. A fiber optic connector, comprising: a ferrule having a front
end, a rear end, and a ferrule bore extending between the front and
rear ends along a longitudinal axis; a ferrule holder from which
the ferrule extends; a housing in which the ferrule holder is
received, wherein the ferrule holder is spring-biased relative to
the housing; and a bonding agent disposed in the ferrule bore and
having first and second ends along the longitudinal axis, wherein:
the bonding agent has been melted and solidified at the first and
second ends; and at least a portion of the bonding agent between
the first and second ends has not been melted and solidified.
19. The fiber optic connector of claim 18, wherein an optical fiber
is not present in the ferrule bore.
20. The fiber optic connector of claim 18, wherein the at least a
portion of the bonding agent between the first and second ends has
not been melted and solidified comprises a powdered material.
Description
BACKGROUND
This disclosure relates generally to optical connectivity, and more
particularly to fiber optic connector sub-assemblies having a
ferrule and bonding agent disposed in the ferrule, along with
methods of making such sub-assemblies.
Optical fibers are useful in a wide variety of applications,
including the telecommunications industry for voice, video, and
data transmissions. In a telecommunications system that uses
optical fibers, there are typically many locations where fiber
optic cables that carry the optical fibers connect to equipment or
other fiber optic cables. To conveniently provide these
connections, fiber optic connectors are often provided on the ends
of fiber optic cables. The process of terminating individual
optical fibers from a fiber optic cable is referred to as
"connectorization." Connectorization can be done in a factory,
resulting in a "pre-connectorized" or "pre-terminated" fiber optic
cable, or the field (e.g., using a "field-installable fiber optic
connector).
Regardless of where installation occurs, a fiber optic connector
typically includes a ferrule with one or more bores that receive
one or more optical fibers. The ferrule supports and positions the
optical fiber(s), which are secured within a bore of the ferrule
using a bonding agent. Some bonding agents have been specifically
developed to allow "pre-loading" the bonding agent into the ferrule
bore prior to a connectorization process. Despite these
developments, there remains room for improvement.
SUMMARY
One embodiment of this disclosure relates to a fiber optic
connector sub-assembly that includes a ferrule having a front end,
a rear end, and a ferrule bore extending between the front and rear
ends along a longitudinal axis. The fiber optic connector
sub-assembly also includes a bonding agent disposed in the ferrule
bore and having first and second ends along the longitudinal axis.
The bonding agent has been melted and solidified at the first and
second ends. Furthermore, in some embodiments at least a portion of
the bonding agent between the first and second ends has not been
melted and solidified.
Another embodiment of a fiber optic connector sub-assembly includes
a ferrule having a front end, a rear end, and a ferrule bore
extending between the front and rear ends along a longitudinal
axis. The ferrule bore includes a first section extending inwardly
from the rear end of the ferrule and having a first width, a second
section extending inwardly from the front end of the ferrule and
having a second width that is less than the first width, and a
transition section located between the first section and the second
section. The fiber optic connector sub-assembly also includes a
bonding agent disposed in at least a portion of both the transition
section and the second section of the ferrule bore. At least some
of the bonding agent in the second section of the ferrule bore has
been melted and solidified.
Methods of making a fiber optic connector sub-assembly are also
disclosed, wherein the fiber optic connector sub-assembly includes
a ferrule having a front end, a rear end, a ferrule bore extending
between the front and rear ends along a longitudinal axis. One
example of such methods comprises: (a) initially disposing a
bonding agent in the ferrule bore; (b) heating at least a portion
of the ferrule above a melting temperature of the bonding agent
initially disposed in the ferrule bore so that some of the bonding
agent melts; and (c) solidifying the bonding agent that has melted
in step (b) to form the fiber optic connector sub-assembly. The
bonding agent has first and second ends along the longitudinal axis
that have been melted and solidified following steps (b) and (c).
Additionally, a portion of the bonding agent initially disposed in
the ferrule bore in step (a) remains below the melting temperature
of the bonding agent during steps (b) and (c) so as to not melt and
solidify during steps (b) and (c).
Another example of methods disclosed herein involves a ferrule
having a front end, a rear end, a ferrule bore extending between
the front and rear ends along a longitudinal axis, wherein the
ferrule bore includes a first section extending inwardly from the
rear end of the ferrule and having a first width, a second section
extending inwardly from the front end of the ferrule and having a
second width that is less than the first width, and a transition
section located between the first section and the second section.
According to this example, the method comprises: (a) initially
disposing a bonding agent in at least the transition section of the
ferrule bore; (b) heating at least a portion of the ferrule above a
melting temperature of the bonding agent initially disposed in the
ferrule bore so that at least some of the bonding agent melts; and
(c) solidifying the bonding agent that has melted in step (b),
wherein at least some of the bonding agent that has been melted and
solidified is disposed in the second section of the ferrule
bore.
Additional features and advantages will be set forth in the
detailed description which follows, and in part will be readily
apparent to those skilled in the technical field of optical
communications. It is to be understood that the foregoing general
description, the following detailed description, and the
accompanying drawings are merely exemplary and intended to provide
an overview or framework to understand the nature and character of
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are included to provide a further
understanding, and are incorporated in and constitute a part of
this specification. The drawings illustrate one or more
embodiment(s), and together with the description serve to explain
principles and operation of the various embodiments. Persons
skilled in the technical field of optical connectivity will
appreciate how features and attributes associated with embodiments
shown in one of the drawings may be applied to embodiments shown in
others of the drawings.
FIG. 1 a perspective view of an example of a fiber optic
connector;
FIG. 2 is an exploded side view the fiber optic connector of FIG.
1;
FIG. 3 is a cross-sectional view of a fiber optic connector
according to another embodiment;
FIG. 4 is a cross-sectional view of an example of a fiber optic
connector sub-assembly for the fiber optic connector of FIG. 2,
wherein the fiber optic connector sub-assembly includes a ferrule
and bonding agent disposed in the ferrule;
FIGS. 5-11 are schematic views that sequentially illustrate an
example of a method of forming a fiber optic connector sub-assembly
according to an embodiment of this disclosure;
FIGS. 12-14 are schematic views illustrating an example of a
heating process for a method of forming a fiber optic connector
sub-assembly according to another embodiment of this
disclosure.
FIG. 15 is a schematic view of one example of an arrangement for
carrying out methods according to some embodiments of this
disclosure.
FIG. 16 is a schematic view of another example of an arrangement
for carrying out methods according to some embodiments of this
disclosure.
FIG. 17 is a schematic view of yet another example of an
arrangement for carrying out methods according to some embodiments
of this disclosure.
FIGS. 18-23 are schematic views that sequentially illustrate a
further example of a method of forming a fiber optic connector
sub-assembly.
DETAILED DESCRIPTION
Various embodiments will be further clarified by examples in the
description below. In general, the description relates to fiber
optic connector sub-assemblies and methods of making the same. The
sub-assemblies and methods may facilitate the cable assembly
process for a fiber optic cable. That is, the sub-assemblies and
methods may be initial steps to facilitate terminating one or more
optical fibers from a fiber optic cable with a fiber optic
connector to form a cable assembly. One example of a fiber optic
connector (also referred to as "optical connector 10", or simply
"connector 10") for such a cable assembly is shown in FIG. 1.
Although the connector 10 is shown in the form of a SC-type
connector, the methods described below may be applicable to
processes involving different fiber optic connector designs. This
includes ST, LC, FC, MU, and MPO-type connectors, for example, and
other single-fiber or multi-fiber connector designs. A general
overview of the connector 10 will be provided simply to facilitate
discussion.
As shown in FIGS. 1 and 2, the connector 10 includes a ferrule 12
having a front end 14 ("mating end") and rear end 16 ("insertion
end"), a ferrule holder 18 having opposed first and second end
portions 20, 22, and a housing 24 (also referred to as "inner
housing 24" or "connector body 24"). The rear end 14 of the ferrule
12 is received in the first end portion 20 of the ferrule holder 18
while the front end 14 remains outside the ferrule holder 18. The
second end portion 22 of the ferrule holder 18 is received in the
housing 24. A spring 26 may be disposed around the second end
portion 22 and configured to interact with walls of the housing 24
to bias the ferrule holder 18 (and ferrule 12). Additionally, a
lead-in tube 28 may extend from a rear end of the housing 24 to
within the second end portion 22 of the ferrule holder 18 to help
guide the insertion of an optical fiber (not shown in FIGS. 1 and
2) into the ferrule 12. An outer shroud 32 (also referred to as
"outer housing 32") is positioned over the assembled ferrule 12,
ferrule holder 18, and housing 24, with the overall configuration
being such that the front end 16 of the ferrule 12 presents an end
face configured to contact a mating component (e.g., another fiber
optic connector; not shown).
In a manner not shown herein, a fiber optic cable providing the
optical fiber also includes one or more layers of material (e.g.,
strength layer of aramid yarn) that may be crimped onto a rear end
portion 30 of the housing 24, which is why the housing 24 may also
be referred to as a "crimp body" or "retention body". A crimp band
(or "crimp ring") may be provided for this purpose. Additionally, a
strain-relieving boot may be placed over the crimped region and
extend rearwardly to cover a portion of the fiber optic cable.
Variations of these aspects will be appreciated by persons familiar
with the design of fiber optic cable assemblies. For example, other
ways of securing a fiber optic cable to the housing 24 are also
known and may be employed in some embodiments. Again, the
embodiment shown in FIGS. 1 and 2 is merely an example of a fiber
optic connector to which the fiber optic connector sub-assemblies
and methods provided in this disclosure may relate.
FIG. 3 illustrates the connector 10 in further detail, and FIG. 4
is an enlarged view of the ferrule 12 in isolation. The ferrule 12
may be the same as that described in U.S. Pat. No. 8,702,322 ("the
'322 patent"), which describes many details related to the geometry
of the ferrule, the location of a bonding agent within a bore of
the ferrule, and possible compositions for the bonding agent, this
information being incorporated herein by reference. In general, the
ferrule 12 includes a ferrule bore 102 extending between the front
and rear ends 14, 16 along a longitudinal axis A1. More
specifically, the ferrule bore 102 has a first section 104
extending inwardly from the rear end 16 of the ferrule 12, a second
section 108 (also referred to as "micro-hole" or "micro-hole
section") extending inwardly from the front end 14 of the ferrule
12, and a transition section 112 located between the first section
104 and the second section 108. The first, second, and transition
sections 104, 108, 112 have respective lengths L1, L2, and L3
measured along or parallel to the longitudinal axis A1. The front
and rear ends 14, 16 define respective front and rear end faces of
the ferrule 12 that extend in planes parallel or substantially
parallel to each other but substantially perpendicular to the
longitudinal axis A1. In some embodiments, the front end face may
be at a slight angle relative to the longitudinal axis A1 to
provide, for example, an angled physical contact (APC) end
face.
Still referring to FIGS. 3 and 4, the first section 104 of the
ferrule bore 102 has a first width, and the second section 108 has
a second width less than the first width such that the transition
section 112 provides a decrease in width between the first section
104 and second section 108. More specifically, in the embodiment
shown, the first section 104 of the ferrule bore 102 is a
cylindrical bore extending from the rear end 16 of the ferrule 12
to the transition section 112 such that the first width is a first
diameter D1. The second section 108 of the ferrule bore 102 is a
cylindrical bore extending from the front end 14 of the ferrule 12
to the transition section 112 such that the second width is a
second diameter D2. Accordingly, the transition section 112
provides a decrease in diameter between the first section 104 and
second section 108.
As shown in FIGS. 3 and 4, a bonding agent 120 is at least
partially located in the transition section 112 of the ferrule bore
102. The bonding agent 120 may be pre-loaded or stored within the
ferrule 100 for a significant amount of time (e.g., at least an
hour, a day, a year, etc.) before inserting an optical fiber into
the ferrule bore 102. For example, as mentioned above, the bonding
agent 120 may be pre-loaded into the ferrule bore 102 by the
manufacturer of the ferrule 100. The combination of the ferrule 12
and bonding agent 120 pre-loaded therein represents a fiber optic
connector sub-assembly 130.
The '322 patent describes how the bonding agent 120 may be a
free-flowing powder material coupled within the transition section
112 of the ferrule bore 102 via compression. Several additional or
alternative steps may be taken, as will be described in greater
detail below, to produce the fiber optic connector sub-assembly in
an even further advantageous manner. First, however, exemplary
bonding agents will be summarized to further provide context for
these additional/alternative steps.
Exemplary Bonding Agents
Although the discussion of possible bonding agents in the '322
patent have been incorporated herein by reference, additional
details relating to such bonding agents can be found in U.S. Pat.
No. 8,696,215 ("the '215 patent") and U.S. Patent Application Pub.
No. 2015/0098679 ("the '679 publication"), such details also being
incorporated herein by reference. Some information from the '322
patent and/or the '215 patent and '679 publication is summarized
below for quick reference.
The bonding agents in the '322 patent, the '215 patent, and '679
publication are configured to be heated and cooled relatively
quickly to facilitate the termination process of a fiber optic
cable, yet are also configured to provide sufficient coupling
between the optical fiber(s) of a fiber optical cable and the
ferrule bore. One specific example of the bonding agent is one that
comprises a partially cross-linked polymer resin and a coupling
agent that provides chemical coupling between the polymer resin and
optical fiber(s), the ferrule 12, or both. The presence of the
coupling agent allows the polymer resin to be selected primarily
for heating and cooling properties rather than adhesion properties.
The bonding agent may even comprise a majority of the polymer resin
so as to be largely characterized by the heating and cooling
properties of the polymer resin. For example, the bonding agent may
comprise between about 0.1 to about 10 parts by weight of the
coupling agent per 100 parts by weight of the partially
cross-linked polymer resin.
As used herein, "cross-linked" or "cross-linking" refers to the
chemical bonding that connects a polymer chain to an adjacent
polymer chain; "partially cross-linked" is where not all adjacent
chains are bonded; and "partially cross-linkable" describes a
chemical species that becomes partially cross-linked when
sufficient heat is applied. It should be understood that the terms
"partially cross-linked" and "partially cross-linkable" describe
the same polymer resin before or after partially cross-linking. For
example, a polymer resin may be described as partially
cross-linkable when it is loaded into a ferrule and has not yet
been heated to a temperature that results in the polymer resin
partially or completely cross-linking.
One example of a partially cross-linkable polymer resin with
desirable heating and cooling characteristics is poly(phenylene
sulfide). One example of a coupling agent having desirable adhesion
characteristics is a coupling agent having a silane functional
group, such as one or more of the following: an alkoxysilane, an
oxime silane, an acetoxy silane, a zirconate, a titanate, a silane
with an epoxy ring on one end and trimethoxy functional group at
the other end, or combinations thereof. Other examples of partially
cross-linkable polymers, coupling agents, and bonding agents are
described in the '322 patent and '215 patents.
As mentioned above, the bonding agent may be a free-flowing powder
material prior to being heated above a cross-linking temperature
for the purpose of securing one or more optical fibers in a
ferrule. The powder may bay a result of grinding various components
of the bonding agent (e.g., the partially cross-linkable resin)
that are initially solid in to respective powders, and then mixing
powders thoroughly together. Some components of the bonding agent
(e.g., the coupling agent) may be a liquid, but the fraction such
components in the blend may be relatively small (e.g., less than 10
parts by weight of the overall blend) so that the resulting blend
is still considered a free-flowing powder. For example, in one
embodiment, the coupling agent may be pre-reacted with the
thermoplastic powders in an organic solvent under refluxing
conditions. After removal of the solvent, the treated powder
remains. Under the conditions of refluxing solvent, some of the
coupling agent may have become permanently bonded to the
polymer.
The partially cross-linkable polymer resin material of the bonding
agent has a melting temperature less than the cross-linking
temperature. For example, the partially cross-linkable polymer
resins above may each have a melting point at temperatures of less
than 250.degree. C., 270.degree., or 290.degree. C., yet each have
a cross-linking temperature (i.e., the temperature at which the
resin materials cross-link in the presence of air) of at least
300.degree. C., 325.degree. C., or even 350.degree. C.
Securing the Bonding Agent
Having described exemplary bonding agents, a method of making the
fiber optic connector sub-assembly 130 (FIG. 4) that includes
additional/alternative steps will now be described with reference
to FIGS. 5-11. The bonding agent 120 may be initially disposed
(i.e., loaded) in the ferrule bore 102 using a loading device 140.
In the embodiment shown, the loading device 140 includes a hollow
tube 142 ("outer rod") and an inner rod 144 that is slidably
received in the tube 142. The loading device 140 is configured to
collect a predetermined amount of the bonding agent 120. Referring
specifically to FIG. 5, the inner rod 144 has an outer diameter
that is substantially the same as (i.e., equal to or within 5% of)
an inner diameter of the tube 142, such that the inner rod 144 is
closely received in the tube 142. The inner rod 144 is initially
set in a retracted position relative to the tube 142 so that a
front end 146 of the inner rod 144 is recessed relative to a front
end 148 of the tube 142. A cavity 150 defined by this recess
corresponds to the predetermined amount of the bonding agent 120 to
collect.
As shown in FIG. 6, the loading device 140 may then be pressed down
into a supply of the bonding agent 120 so that the cavity 150 is
packed or otherwise filled with the bonding agent 120. The loading
device 140 may then be positioned next to the ferrule 12 (FIG. 7)
with the cavity 150 aligned with the ferrule bore 102. After
contacting the rear end 16 of the ferrule 12 with the front end 148
of the tube 142 (FIG. 8), the inner rod 144 may be advanced/moved
relative to the tube 142 and into the ferrule bore 102 (FIG. 9) to
move the bonding agent 120 into a desired location within the
ferrule bore 102. As mentioned above, examples of desirable
locations of the bonding agent 120 within the ferrule bore 102 are
discussed in the '322 patent and incorporated herein by
reference.
Before or after removing the loading device 140 from the ferrule
12, at least a portion of the ferrule 12 may be heated above a
melting temperature of the bonding agent 120. FIG. 10 schematically
illustrates the ferrule 12 being heated at first and second
locations by first and second heating sources 160, 162. The first
location may generally correspond to the beginning of the
micro-hole section 108 of the ferrule bore and/or a first end 164
of the bonding agent 120 (i.e., the first location may be a
location on an outer surface 170 of the ferrule 12 that is
substantially the same distance from the front end 14 as the
beginning of the micro-hole section 108 and/or the first end 164 of
the bonding agent 120). The second location may generally
correspond to a second end 166 of the bonding agent 120 (i.e., the
second location may be a location on the outer surface 170 of the
ferrule 12 that is substantially the same distance from the front
end 14 as the second end 166 of the bonding agent 120).
Alternatively or additionally, the second location may generally
correspond to the end of the first section 104/beginning of the
transition section 112.
In other embodiments, the ferrule 12 may be heated at only a single
location or at more than two locations, and there may be only a
single heating source or more than two heating sources. The ferrule
12 may alternatively or additionally be moved relative to one or
more heating sources, or vice-versa, to heat a portion of the
length of the ferrule 12 in a more continuous manner. Specific
examples relating to the above-mentioned possibilities will be
described in more detail below.
Regardless of how the ferrule 12 is heated with the one or more
heating sources, some of the bonding agent 120 melts as a result of
the heating process. In particular, at least the first and second
ends 164, 166 of the bonding agent 120 melt. The melted bonding
agent is then allowed to cool (either passively or actively) to
solidify. FIG. 11 illustrates how the portion of the bonding agent
120 that has been melted and solidified may form a solid crust 172
("crust portion") around a portion 174 of the bonding agent that
has not been melted and solidified. The crust portion 172 of the
bonding agent 120 is no longer in a powder form. There is some
crystallinitiy in the crust portion (e.g., the crust portion may
have a spherulipic crystallinity of about 20-60%).
The other portion 174 of the bonding agent 120, on the other hand,
remains in a powder form in this embodiment (and, therefore, may be
referred to as the "powder portion" or "powder material" of the
bonding agent). For example, the powder portion 174 may still
comprise particles of the bonding agent 120 material having an
average size (e.g., maximum diameter or width) between 8 and 100
microns. The powder portion 174 is not crystalline (and not
quenched), and instead is amorphous.
There are various ways to characterize the difference between the
crust portion 172 and powder portion 174 other than the distinction
between a solid region and powder region. For example, the crust
portion 172 may have a density between about 1.0 grams per cubic
centimeter (g/cc) and 1.5 g/cc (and specifically between about 1.3
g/cc and 1.4 g/cc in some embodiments), whereas the powder portion
174 may have a bulk or untapped density that is less, such as
between about 0.4 and 0.6 g/cc. Stated differently, the crust
portion 172 may have a density that is at least 1.5, 2, or even 3
times the bulk/untapped density of the powder portion 174.
There are also various ways to characterize the extent of the crust
portion 172. For example, the bonding agent 120 has an axial length
l.sub.0 measured along the longitudinal axis A1 between the first
and second ends 164, 166. The first and second ends 164, 166 may be
part of respective first and second regions of the bonding agent
120 that each represent between about 1% and about 33% of the
overall axial length l.sub.0 of the bonding agent 120. Stated
differently, and as shown in FIG. 11, the first and second regions
may have respective axial lengths l.sub.1 and l.sub.2 that are
between about 1% and about 33% of the overall axial length l.sub.0.
The first and second regions may alternatively be characterized
with reference to the diameter D1 (FIG. 4) of the first section 104
of the ferrule bore 102. For example, the first and second regions
have respective axial lengths l.sub.1 and l.sub.2 that are each
between about 1% and about 50% of the outer diameter D1. In some
embodiments (including any of those mentioned above), at least 90%
of the bonding agent 120 in the first region has been melted and
solidified (i.e., is in the form of crust portion 172). In these or
other embodiments, at least 90% of the bonding agent 120 in the
second region has been melted and solidified (i.e., is in the form
of crust portion 172).
As shown in FIG. 11, the crust portion 172 may even be formed in a
peripheral region of the bonding agent 120 that is between the
first and second ends 164, 166 and in contact with the surface of
the ferrule bore 102. The powder portion 174 then comprises a
central region of the bonding agent 120 surrounded by the
peripheral region. In some embodiments, the crust portion 172 may
have a thickness T between about 1% and about 30% of the outer
diameter D1 (FIG. 4; the thickness T is measured from where the
bonding agent 120 contacts the surface of the ferrule bore 102 to
the nearest location of the crust portion 172). Although FIG. 11
illustrates the crust portion 172 being formed around an entire
periphery of the bonding agent 120, in some embodiments only the
first and second ends 164, 166 of the bonding agent 120 may form a
crust portion.
As can be appreciated, by forming the crust portion 172 in at least
the first and second ends 164, 166 of the bonding agent 120, the
bonding agent 120 is more securely coupled to the ferrule bore 102
compared to the situation where no amount of the bonding agent 120
has been melted and solidified. This helps preserve the
predetermined amount of the bonding agent 120 in the ferrule bore
102 between the time of forming the fiber optic connector
sub-assembly 130 and the time when the fiber optic connector
sub-assembly 130 is used during a cable assembly/termination
process. The period between times may be significant, such at least
a day, a week, a month, or even a year. And during this period, the
fiber optic connector sub-assembly 130 may be transported and
otherwise handled in various manners. The likelihood of the bonding
agent 120 migrating out of the ferrule 12 during this period may be
reduced or eliminated by forming the fiber optic connector
sub-assembly 130 in the manner described above.
In addition to helping preserve the predetermined amount of the
bonding agent 120 in the ferrule bore 102, forming the crust
portion 172 also helps preserve the bonding agent 120 in the
location where the bonding agent 120 is initially disposed in the
ferrule bore 102. The improvement in consistency simplifies or
otherwise facilitates termination processes involving the fiber
optic connector sub-assembly 130.
Furthermore, when the bonding agent 120 comprises a partially
cross-linkable polymer resin, the heating of the bonding agent 120
may be carefully controlled so that the crust portion 172 melts and
solidifies without irreversible chemical bonding between adjacent
polymer chains of the polymer resin. This may be achieved by
heating the ferrule 12 (and, ultimately, portions of the bonding
agent 120) above the melting temperature of the bonding agent, but
below the cross-linking temperature of the bonding agent. One of
the advantages of such a process is that the resulting fiber optic
connector sub-assembly 130 not only has the bonding agent 120 more
securely coupled to the ferrule bore 102, but also preserves the
ability of the bonding agent 120 to form even greater adhesion
properties at a later point in time. In particular, the
irreversible cross-linking and greatest adhesion properties of the
bonding agent 120 can be reserved for the cable
assembly/termination process in which the fiber optic connector
sub-assembly 130 is eventually used.
Now that methods of forming the fiber optic connector sub-assembly
130 have been introduced, some more specific examples relating to
the heating process will be described. The first and second heating
sources 160, 162 in FIG. 10 are shown in a generic manner because
any suitable heating source may be used to heat the ferrule 12. For
example, the heating source(s) associated with the heating process
may comprise one or more laser(s), oven(s), resistive wire(s)
wrapped around the ferrule, or the like.
In the embodiment shown in FIGS. 12-14, a single heating source
represents a laser 180 that is first used to irradiate the ferrule
12 at the first location. If desired, the ferrule 12 may be rotated
relative to the laser 180, or vice-versa, to irradiate all or
portions of the circumference of the ferrule 12 at the first
location. Relative axial movement may then be initiated between the
ferrule 12 and laser 180 (i.e., the ferrule 12 may be moved
relative to the laser 180, or vice-versa, in a direction along or
parallel to the longitudinal axis A1) to bring a beam of the laser
180 into alignment with the second location. At this point, and as
schematically shown in FIG. 13, the laser 180 may then be operated
to irradiate the ferrule 12 at the second location. Again, if
desired, the ferrule 12 may be rotated relative to the laser 180,
or vice-versa, to irradiate all or portions of the circumference of
the ferrule 12.
One of the advantages of irradiating the ferrule 12 at two or more
axial locations is that the bonding agent 120 can be more
strategically melted. For example, attempting form a laser beam
that spans a length between the two locations may not lead to
uniform (or at least as uniform) melting of the bonding agent 120
where the melting is needed most--namely, the first and second ends
164, 166 of the bonding agent--to provide the above-mentioned
benefits. This, in turn, may result in air voids or other
undesirable attributes in the crust portion 172. Nevertheless, the
present disclosure does not exclude forming a laser beam that spans
a length of the ferrule 12 corresponding to a greater portion or
all of the axial length l.sub.0 (FIG. 11) of the bonding agent
120.
FIGS. 15-17 schematically illustrate various ways one or more
lasers 180 may be arranged relative to the ferrule 12. In FIG. 15,
a reflector 182 is used to direct a laser beam 184 at the ferrule
12, which may allow the laser 180 to be positioned in an optimized
manner. In FIG. 16, first and second lasers 180a, 180b are used to
emit respective first and second beams 184a, 184b that impinge
opposite sides of the ferrule 12. Such an arrangement may be an
effective way to heat the ferrule 12 and melt some of the bonding
agent 120 without relative rotation between the ferrule 12 and one
or more lasers, although such relative rotation may still be
initiated if desired. FIG. 17 illustrates an arrangement similar to
FIG. 16, except that only a single laser 180 is used to irradiate
opposite sides of the ferrule 12. The laser 180 emits a laser beam
190 that is split into two beam portions 190a, 190b (or "legs") by
a beam splitter 192, with each beam portion 190a, 190b being
directed by one or more reflectors 182 to impinge opposite sides of
the ferrule 12. Optical elements, such as lenses, may be positioned
anywhere in the path of the beam portions 190a, 190b to shape or
otherwise focus the beam portions 190a, 190b in a particular way,
if desired.
Each of the arrangements in FIGS. 15-17, or variants thereof, may
be used to heat the ferrule 12 at both the first and second
locations, analogous to the single laser 180 in the embodiment
discussed with reference to FIGS. 12-14. Alternatively, there may
be a separate and distinct setup or arrangement of one or more
lasers for heating the ferrule 12 at the first and second
locations. For example, the ferrule 12 may be positioned relative
to a first arrangement of one or more lasers, heated at a first
location, moved and positioned relative to a second arrangement of
one or more lasers, and then heated at a second location. The first
and second arrangements may be the same or different
arrangements.
Filling the Micro-Hole of the Ferrule Bore
In some instances, it may be desirable to fill the second section
108 of the ferrule bore 102 with the bonding agent 120 when forming
the fiber optic connector sub-assembly 130. For example, in some
embodiments the front end 14 of the ferrule 12 may be grinded or
otherwise re-shaped prior to being installed on an optical fiber to
form an end face with a specific geometry (e.g., an angled physical
contact (APC) end face). Such additional processing has the
potential to deposit debris in the second section 108, which can
make inserting an optical fiber during a later termination process
challenging (and even impossible in some instances). Even if there
is no additional processing, the ferrule 12 may be exposed during
normal handling and transport to debris that also has the potential
to migrate into and block the second section 108. Filling the
second section 108 of the ferrule bore 102 may also help ensure
that an optical fiber terminated with the ferrule 12 is surrounded
by the bonding agent 120 within the second section 108 after the
termination process. This, in turn, can improve adhesion strength
and reliability.
One of the challenges in filling the second section 108 of the
ferrule bore 102 with the bonding agent 120 relates to the
relatively small size of the ferrule bore 120. Simply loading the
bonding agent 120 into the ferrule bore 102 in the manner described
above may not result in a sufficient amount of the bonding agent
120 occupying the second section 108. This may especially be the
case when the bonding agent 120 is initially disposed in the
ferrule bore 102 in a powder form, as the solid nature and size of
particles in such a material may make it difficult to locate the
bonding agent 120 in the second section 108 of the ferrule bore
102. Moreover, even if there can be a substantial amount of the
bonding agent 120 initially disposed in the second section 108 in
alternative embodiments, it is still desirable to melt and solidify
at least some of the bonding agent 120 for the reasons mentioned
above.
One example of a method for making the fiber optic connector
sub-assembly 130 with more bonding agent disposed in the second
section 108 of the ferrule bore 102 is shown in FIGS. 18-23. The
bonding agent 120 may be initially disposed in the ferrule bore 102
in the manner described above with reference to FIGS. 5-9 (e.g.,
using the loading device 140) or in any other manner. The bonding
agent 120 is initially disposed in the transition section 112 of
the ferrule bore 102, although there may be some amounts also
disposed in the first and second sections 104, 108 in some
embodiments, as shown in FIG. 18. The amount of the bonding agent
120 initially disposed in the second section 108 in such
embodiments may be relatively small. For example, the bonding agent
120 initially disposed in the ferrule bore 102 may occupy less than
50%, less than 25%, or even less than 10% of the volume of the
second section 108 in some embodiments.
To assist moving more of the bonding agent 120 into the second
section 108 of the ferrule bore 102 before or during a heating of
the ferrule 12, a nozzle 200 may be coupled to the rear end 16 of
the ferrule 12. FIG. 19 schematically illustrates the nozzle 200
including an outlet 202 communicating with the ferrule bore 102 at
this point. Pressurized air or other gas may be supplied through
the nozzle 200 and into the ferrule bore 102 to apply pressure to
the bonding agent 120. The pressure can help force at least some of
the bonding agent 120 from the transition section 112 into the
second section 108, especially after heating and melting at least
some of the bonding agent 120.
To this end, FIGS. 20-22 schematically illustrate the ferrule 12
being heated at first and second locations by a heating source 160.
The heating may be achieved using any of the principles discussed
above. For example, there may alternatively be first and second
heating sources like the embodiment in FIG. 10. The various methods
of heating, including the different types, arrangements, and
operation of heating sources discussed with reference to FIGS. 10
and 12-17, remain possibilities. The heating source 160 may
represent one or more lasers, for example. In such embodiments, the
laser beam(s) may even be focused using lenses or other optical
elements to impinge over a longer length of the ferrule 12. This
may be particularly advantageous for the heating source 160, as
heating both a portion of the transition section 112 and a portion
of the second section 108 when heating the ferrule 12 at the first
location may help promote flow of the bonding agent 120 that has
melted into the second section 108.
As can be seen in FIGS. 20 and 21, at least some of the bonding
agent 120 melts after heating the ferrule at a first location with
the heat source 160, and the melted bonding agent 120 eventually
solidifies (e.g., through passive or active cooling) in the second
section 108 of the ferrule bore 102. In the embodiment shown, at
least some of the bonding agent 120 initially disposed in the
transition section 112 has melted and flowed into the second
section 108. As a result, there is an increased amount of the
bonding agent 120 in the second section 108. Indeed, in some
embodiments, the bonding agent 120 may occupy at least 90% of the
volume of the second section 108 following the heating and
solidification.
The flow of the bonding agent 120 may be assisted by the pressurize
air supplied by the nozzle 200, as noted above. The nozzle 200 acts
as an air coupling, forming a seal with the ferrule bore 102. The
supply (not shown) of air or other gas to the nozzle 200 may be
turned on before the heating source 160 to apply pressure before
heating, and turned off shortly prior to or when the heating source
160 is activated. Alternatively, the supply may be kept on for a
period of time while the heating source 160 is in operation. Other
methods of applying pressure to the bonding agent 120 before or
during the heating step will be appreciated. Additionally, rather
than supplying pressurized air with a nozzle, in some embodiments a
vacuum (not shown) may be coupled to the front end 14 of the
ferrule 12 over the opening of the ferrule bore 102. The vacuum may
be operated to assist at least some of the bonding agent 120 that
has melted in the transition section 112 to flow into the second
section 108 of the ferrule bore 102.
In some embodiments, the heating source 160 may be controlled based
on the flow of the bonding agent 120 into the second section 108 of
the ferrule bore 102. For example, equipment may be used to monitor
when some of the bonding agent 102 reaches or exits the end of the
ferrule bore 102. The heating source 160 may then be deactivated in
response to the detection of the bonding agent 120. This may help
ensure that the heating process has been carried out long enough
for the bonding agent 120 to substantially or completely occupy the
second section 108 of the ferrule bore 102.
As can be appreciated from FIGS. 21 and 22, eventually the ferrule
12 is heated at the second location, similar to the embodiment
discussed above with respect FIG. 10, to melt an additional amount
of the bonding agent 120. Like the embodiment in FIG. 10, the
additional amount of the bonding agent 120 heated at this stage was
initially disposed in the ferrule bore 102. In alternative
embodiments not shown, there may only be a small amount of the
bonding agent 120 initially disposed in the ferrule bore 102. After
heating the first location of the ferrule 12 to melt some or all of
this small amount, and after allowing the melted bonding agent 120
to solidify in the second section 108 of the ferrule bore 102
(similar to FIGS. 20 and 21), an additional amount of the bonding
agent 120 may be loaded into either or both the first section 104
and the transition section 112 of the ferrule bore 108. The ferrule
12 may then be heated at the second location to melt at least some
of this additional amount. Either way, the additional amount of the
bonding agent 120 that melts when heating the ferrule 12 at the
second location is eventually cooled and solidified in either or
both the first section 104 and the transition section 112 of the
ferrule bore 102.
FIG. 23 illustrates the fiber optic connector sub-assembly 130
resulting from the process shown in and described with reference to
FIGS. 18-22. As can be appreciated, the bonding agent that has been
melted and solidified can still form a crust portion 174 around a
portion 174 of the bonding agent that has not been melted and
solidified. In this regard, the fiber optic connector sub-assembly
remains similar to the one discussed above with reference to FIG.
11, except that an increased amount of the bonding agent 120
occupies the second section 108 of the ferrule bore 102. Again, the
bonding agent 120 may substantially or entirely occupy the second
section 108 as a result of the process shown in and described with
reference to FIGS. 18-22. Most or all of the bonding agent 120 in
the second section 108 may be part of the crust portion 172. For
example, at least 90% of the bonding agent 120 disposed within the
second section 108 of the ferrule bore 102 may have been melted and
solidified.
The portion 174 that has not been melted and solidified may be a
powder portion 174, as mentioned above, when the bonding agent 120
is initially disposed in the ferrule bore 102 in a powder form.
Therefore, the various ways of characterizing the difference
between the crust portion 172 and powder portion 174 mentioned
above (e.g., differences in crystallinity and/or density) remain
applicable.
Persons skilled in optical connectivity will appreciate additional
variations and modifications of the elements disclosed herein. Such
persons will also appreciate variations and modifications of the
methods involving the elements disclosed herein. For example,
although embodiments are described above where less than all of the
bonding agent is heated and solidified when forming a fiber optic
connector sub-assembly, in alternative embodiments all or
substantially all of the bonding agent may be heated and
solidified. In such embodiments, the heating may still be
controlled so that the bonding agent does not irreversibly
cross-link and/or end up with a high degree of crystallinity (e.g.,
a spherulipic crystallinity above 60%). For example, when the
bonding agent comprises a partially cross-linkable polymer resin
like the ones disclosed here, the bonding agent may be heated to
above 250.degree. C. but kept below 350.degree. C., or even
300.degree. C.
In addition to appreciating these and other variations, skilled
persons will appreciate alternatives where some of the steps
described above are performed in different orders. To this end,
where a method claim below does not actually recite an order to be
followed by its steps or it is not otherwise specifically stated in
the claims below or description above that the steps are to be
limited to a specific order, it is no way intended that any
particular order be inferred.
* * * * *